This invention relates to an electro-optical transducer module and a method of fabricating such a module.
U.S. Pat. No. 4,722,586 issued Feb. 2, 1988 to Dodson et al discloses a method of fabricating an electro-optical transducer module in which a metal diode mount is brazed to a layer of metallization on a planar reference surface of a multilayer ceramic body, and a laser diode is secured to the top of the diode mount by soldering. An end region of a single mode optical fiber is stripped of its protective jacket, metallized, and soldered to the top face of a ceramic fiber mount. A drop of solder cream is placed on the reference surface of the multilayer ceramic body. The fiber mount, which serves the dual purpose of rigidizing the end region of the fiber and providing a handling element that can be gripped using a micromanipulator of conventional form, is placed with its bottom face in contact with the solder cream and is positioned so that the end face of the fiber is optically coupled to the light-emitting region of the diode. When the fiber mount is properly positioned, the solder cream is heated and is allowed to cool, whereupon it bonds the fiber mount to the ceramic body.
In order to achieve satisfactory optical coupling between a single mode fiber and a laser diode, a tolerance of only about 0.1 .mu.m is permitted on positioning the end face of the fiber relative to the diode in all three linear degrees of freedom. A disadvantage of the electro-optical transducer module disclosed in U.S. Pat. No. 4,722,586 is that the fiber mount and the diode mount result in the end face of the optical fiber and the light-emitting region of the diode both being spaced at a substantial distance from the reference surface of the ceramic body, and therefore any difference in coefficient of thermal expansion between the fiber mount and the diode mount can result in significant change in the relative positioning of the end face of the fiber and the light-emitting region of the diode, and consequent degradation of coupling between the fiber and the diode, when the module is exposed to a change in temperature.